Heat exchange apparatus having additional conducting paths



P. A. M CUEN July 6, 1965 HEAT EXCHANGE APPARATUS HAVING ADDITIONAL CONDUCTING PATHS Filed July 3, 1961 INVENTOR. PETER A. MC CUEN BY a;

ATTORNEY United States Patent 3,193,003 HEAT EXCHANGE APPARATUS HAVING ADDETIGNAL CONDUQTING PATHS Peter A. McCucn, Palo Alto, Calif., assignor to Varian Associates, lalo Alto, Calif., a corporation of California Filed July 3, 1961, Ser. No. 121,724 5 Claims. (Cl. 165-185) The present invention relates in general to electron devices and more particularly to methods and apparatus for efiiciently cooling electrodes thereof.

In electron devices such as, for example, traveling wave tubes, klystron tubes, and magnetrons it becomes necessary to cool certain portions of the tube. Typically, in traveling wave tubes and klystrons, heat is generated in the collector electrode, and in a magnetron heat is generated in an anode structure. It has been customary to cool such devices by providing a plurality of cooling fins extending radially circumferentially or radially axially on the hot electrode and then passing a cooling fluid such as air over these fins.

In order to increase the heat transfer from a hot component to a colder cooling fluid it is helpful to increase the area over which the heat transfer occurs. This has led to the practice of increasing the size and the number of fins.

Since the heat transfer from the fins to the cooling fluid is proportional to the product of the fin area and the finfluid temperature differential, by enlarging the fins the increase in heat transfer will not be directly proportional to the increase in heat transfer area because the temperature everywhere along the fins will not be equal to that at the fin root or immediately adjacent the hot electrode. Thus, the increased heat transfer due to increased area is partly offset by the decreased average fin-fiuid temperature differential.

According to the present invention a high conductance heat path is provided from the hot electrode to an outer portion of the cooling fins which are secured to the hot electrode. In this manner the temperature of the fins is maintained approximately uniform and approximately the same temperature as the hot electrode for more efficient cooling of the electrode.

The principal object of the present invention is to provide novel method and apparatus for efiiciently cooling hot elements of electron devices.

One feature of the present invention is the provision of a novel cooling means for an electron device including a high thermal conductance path from a hot element of the electron device to an outer portion of cooling fins on the element.

Another feature of the present invention is the provision of novel cooling means for an electron device including a high thermal conductance member extending radially outwardly from the hot element and axially ex tending high thermal conductance means connecting said high conductance member to an outer portion of said fins.

Another feature of the present invention is the provision of a novel cooling apparatus for an electron device including a high thermal conductance member extending radially outwardly between at least two radially extending axially aligned fins and circular high thermal conductance means connecting said high thermal conductance member to an outer portion of said fins.

Other features and advantages of the present invention will become more apparent upon a perusual of the following description taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a sectional view of a traveling wave tube embodying the present invention,

ice

FIG. 2 is a cross sectional view of the structure shown in FIG. 1 taken along line 22 in the direction of the arrows, and

FIG. 3 is an end view of an alternative embodiment of the present invention.

Whereas the invention will be described as specifically applied to a traveling wave tube type of electron device it is obvious that the invention is equally applicable to any electron device having a metallic member constituting an outside portion of the tube envelope such as, for example, a klystron tube, a magnetron, etc.

Referring to FIGS. 1 and 2 of the drawing, a traveling wave tube amplifier 11 includes an evacuated envelope 12 at one end of which is positioned an electron gun structure 13 including a cathode 14- and associated cylindrical anode 15 adapted for generating a beam of electrons. Positioned at the other end of the evacuated envelope 12 is a collector electrode structure 16 adapted to receive the electron beam generated by the electron gun structure 13.

Between the electron gun structure 13 and the collector electrode structure 16 is a slow wave structure shown, for example, as a helix 17 mounted on a plurality of sapphire support rods 18 which are fitted within the envelope 12.

A ralio frequency energy input coupling means 19 is provided at the electron gun end of the envelope 12 for applying a radio frequency wave to the slow wave helix 17, and a radio frequency output coupling means 21 is provided at the collector end of the envelope 12 for extracting an amplified radio frequency wave from the slow Wave helix 17.

A beam focusing solenoid 22 is positioned around the evacuated envelope 12.

The colector electrode structure 16 comprises a hollow, high thermal conductance core member 24- of, for example, copper the exterior end of which is terminated by an evacuation pinch-off tube 25 molded into an insulator plug 26. A thermally conductive cylinder 27 surrounds and is fixedly secured to the core member 24 and is provided with a plurality of radially directed annular cooling fins 28 which provide a large area for the transfer or" heat to a surrounding cooling fluid such as circulating air.

High thermal conductance members 2 of, for example, copper and in the form of solid rings are each positioned between and fixedly secured to two of the fi r fs 28 and form a low thermal resistance path from the cylinder 27 to an outer region of the cooling fins 28. Connection means 31 of, for example, copper in the form of narrow ring segments with an outside diameter that of members 29 and a slightly smaller inside diameter are positioned between and fixedly secured to adjacent cooling fins 28 thereby forming a low thermal resistance path from the member 29 to an outer portion of all the fins 28. By this construction the entire fin can be maintained at approximately a uniform temperature and at approximately the temperature of the core member 24 for the most efficient heat exchange between the cooling fins 2.8 and the cooling fluid.

b As an example of the advantages of the present invention the amount of heat transferred by one collector structure of the type described above was 40% greater than the heat transferred by a finned collect-or without the ad ditional high conductance structure.

As an alternative to the structure shown the members 29 can be positioned at the end of the collector structure 16 adjacent the cathode to draw off heat from the hottest portion of the collector. Also the connection means 31 can conveniently take the form of rods axially extending the length of the collector and extending throughv and member 24 in FIGS. 1 and 2 is cooled by means of a 'plu rality of radially extending longitudinally directed fins 42 secured such as by braiing to the metallic member 41 and separated from one another by spacer, members 43. High thermal conductance, members 44 of, for example, copper are provided between certain of the fins 42 for providing a low thermal resistance path from the metallic member 41 to an outer region of the fins'4-2'. High conductance connection means 45 which take the form of circular rings of, for example, copper are connected to the outer end of the members 44 and to all of the fins 42 for conducting heat from the members 44 to an outer portion of each of the fins 42.v In this manner each of the fins 42 is maintained at approximatelya uniform temperature and at approximately the temperature of the metallic member 41 for the most efiicient heat exchange between fins 42 and the cooling fluid.

The metallic member 41 and the core member 24 could be any hot element of an electron device which must be cooled as, for example, the body portion of the envelope 12.

Underconditions of constant fin cross sectional area and constant convective heat transfercoefi'icient between the fins andthe cooling fiuidthe position at which the high conductance means 31 and contact the'cooling fins 28 and 42, respectively, is approximately two-thirds of the radial fin length in a direction outward from the fin root in order to maintain the temperature of the fin 7' approximately uniform. Since there is a limited heat conductance path through the high conductance members 29 and 44 and the connection means 31 and 45 this distance can be made somewrat greater than two-thirds in order to achieve an even more uniform temperature along the fins.

of a constant cross sectional area.

Since. many changes can be made in the structure set The best outward distance along the fins for the connection means would be different if the fins are'not forth above without departing from the scope of the pressaid metallic member to an outer portion of said fins, the

thermal resistance of said first means being less than the thermal resistance of any one of saidplurality of; fins, :and second means forming a low thermal resistance path, said second means being spaced from said metallic member and coupled to said first means and to said fins whereby the temperature of each of said fins is maintained approximately uniform over the entire fin.

2. Cooling apparatus for an electron device comprising, a metallic member defining a longitudinal axis, a plurality of fins radiating from said metallic member, first means substantially transversely oriented with respect to said longitudinal axis forming a low thermal resistance path tfromsaid electrode to an outer portion of said fins, said first means having a lower thermal resistance than any one of said fins, and second means forming a low thermal resistance path, said second means being spaced from said metallic electrode and coupled to said first means and to said fins whereby the temperature of each of said fins is maintained approximately'uniform over the entirefin, said cooling apparatus being adapted and arranged to permit flow of cooling fluid between said plurality of fins.

3. Cooling apparatus for an electron device comprising, a metallic element a plurality of annular fins rad-iating outwardly from said metallic element, a high thermal conductance member positioned between and fixedly securedto at least two. of said fins and extending radially outwardly from said metallic element, and axially extending, high conductance connection'means connecting said high conductance'member to an outer portion of said fins, the thermal conducti'vityof said high thermal conductance connection means being greater than the thermal conductivity of any onewof said fins, said high conductance connection means being spaced from said metallic element whereby the temperature of said fins is maintained approximately uniform over the entire fin.

4. Cooling apparatus for an electron device comprising,

in a metallic element, a plurality of fins radiating from said metallic element and extending axially thereof, at least one high thermalconductance member positioned 'between and fixedly secured to, at least two of said fins,

and circular, high conductance connection means connecting said high conductance .member to an outer portion of said fins, said high conductance connection means "being spaced from said metallic element to permit the flow of, acooling fluid between said fins, said metallic element, and said high conductance connection means whereby the temperature of each of said fins is maintained approximately uniform over the entire fin.

5. Cooling mean-s for an electron device comprising, a metallic electrode defining a longitudinal axis, a plurality of fins attached to and radiating from said'metallic electrode' along the length of said elect-rode, first means forming a low thermal resistance path connected to said metallic electrode and to at least two of said fins, said first means having a lower thermal resistance t-hanany one of said plurality of fins, second means forming a low thermal resistance path outwardly spaced from said metallic electrode and connected to said first means and to said fins at an outer portion of said fins and extending along the length of said electrode, said first and said second means functioning to maintain the temperature of each of said fins approximately uni-form over the entire fin.

References Cited by the Examiner UNiTED STATES PATENTS 1,854,278. 4/32 Smith.

2,460,575 2/49 Hanson'et al.' 313-46 2,653,800 9/53 Anton 183 X 2,680,209 6/54 Veronda 3l3--46 X 2,713,997 7/55 Ruckstell.

2,770,745 11/ 56 Manfredi 31344 I FOREIGN PATENTS 1 607,459 .,7/26 France.

137,352 9/01 Germany. 265,698 3/13' Germany. 569,259 11/57 Italy.

GEORGE N. WESTBY, Primary Examiner. RALPH G.NILSON, Examiner. 

1. COOLING APPARATUS FOR AN ELECTRON DEVICE COMPRISING, A METALLIC MEMBER DEFINING A LONGITUDINAL AXIS, A PLURALITY OF FINS RADIATING FROM SAID METALLIC MEMBER, FIRST MEANS SUBSTANTIALLY TRANSVERSELY ORIENTED WITH RESPECT TO SAID LONGITUDINAL AXIS FORMING A LOW THERMAL RESISTANCE PATH FROM SAID METALLIC MEMBER TO AN OUTER PORTION OF SAID FINS, THE THERMAL RESISTANCE OF SAID FIRST MEANS BEING LESS THAN THE THERMAL RESISTANCE OF ANY ONE OF SAID PLURALITY OF FINS, AND SECOND MEANS FORMING A LOW THERMAL RESISTANCE PATH, SAID SECOND MEANS BEING SPACED FROM SAID METALLIC MEMBER AND COUPLED TO SAID FIRST MEANS AND TO SAID FINS WHEREBY THE TEMPERATURE OF EACH OF SAID FINS IS MAINTAINED APPROXIMATELY UNIFORM OVER THE ENTIRE FIN. 